1. Field of the Invention
The present invention relates generally to catheters and methods of treating the stenosis of an artery. In particular, the present invention relates to catheters and methods for accessing chronic total occlusions (CTOs) in arteries caused by the buildup of arterial plaque tissue.
2. Description of the Related Art
Chronic total occlusion (CTO) is a condition where arterial plaque tissue grows to complete stenosis of an artery and prohibits blood flow. A CTO is formed by the agglomeration of three separate physiological materials: (i) cholesterol or fat, (ii) collagen or fibrous matter, and (iii) calcium-based deposits. A CTO is also often referred to as a functional occlusion.
There are two causal pathogenic phenomena often associated with the formation of a CTO. The first is the late development of an acute occlusion. The second is the progressive occlusion of a long-term high degree stenosis. Both involve a pre-existing plaque or thrombus to which the fat and fibrous material adhere, building up until a blockage of the blood vessel occurs. A CTO 10 will sometimes form in a side branch 11 of an artery 12 as shown in FIG. 1, which is difficult to access using conventional catheters and surgical techniques.
Physicians currently attempt to perforate CTOs 10 in side branches 11 using a stiff guide wire 13 as shown in FIG. 2. A small catheter 14 is used to position the guide wire 13 at the occlusion 10.
Another conventional technique involves the use of a curved catheter 15 to align a perforating guide wire 16 with the angle of the side branch 11, as shown in FIG. 3. One of the primary problems with this approach occurs when a compressive force is applied to the guide wire 16. The guide wire 16 must be pushed to perforate the occlusion 10 and as it is pushed, the catheter 15 in which the guide wire 16 is contained reacts in a negative manner, as shown in FIG. 4. As can be seen, the catheter 15 will be pushed and/or rotated away from the side branch 11, or misaligned with the side branch 11, as compressive force is exerted on the guide wire 16. The restraint offered by the catheter 15 is limited because it must be made of a material that is soft enough not to injure the arteries as it is advanced into the vascular system. Catheters are limited as to the amount of stiffness the catheter can contain before it will injure the artery as it is aligned with the side branch. In addition, the curvature of the catheter can cause substantial “whip” as a physician torques the catheter to align it with the side branch.
A compliant balloon 17 can be attached to the catheter 18 to help limit the reaction forces on the catheter 18, as shown in FIG. 5. The balloon 17 is inflated through a separate lumen in the catheter 18. The balloon 17 allows for more stability in the catheter 18 as it is used. However, it still suffers from the cantilever type positioning exhibited in FIG. 4. In addition, it is still subject to whip caused by the curvature of the catheter as torque is applied to position the catheter.
There is a need in the industry for improved devices and methods to assist surgeons in accessing CTOs in side branches of arteries.